Featured Research

from universities, journals, and other organizations

Color Perception Is Not In The Eye Of The Beholder: It's In The Brain

Date:
October 26, 2005
Source:
University of Rochester
Summary:
First-ever images of living human retinas have yielded a surprise about how we perceive our world. Researchers at the University of Rochester have found that the number of color-sensitive cones in the human retina differs dramatically among people -- by up to 40 times -- yet people appear to perceive colors the same way. The findings strongly suggest that our perception of color is controlled much more by our brains than by our eyes.

Images of living human retinas showing the wide diversity of number of cones sensitive to different colors.
Credit: Photo credit: University of Rochester

First-ever images of living human retinas have yielded a surprise about how we perceive our world. Researchers at the University of Rochester have found that the number of color-sensitive cones in the human retina differs dramatically among people—by up to 40 times—yet people appear to perceive colors the same way. The findings, on the cover of this week's journal Neuroscience, strongly suggest that our perception of color is controlled much more by our brains than by our eyes.

Related Articles


"We were able to precisely image and count the color-receptive cones in a living human eye for the first time, and we were astonished at the results," says David Williams, Allyn Professor of Medical Optics and director of the Center for Visual Science. "We've shown that color perception goes far beyond the hardware of the eye, and that leads to a lot of interesting questions about how and why we perceive color."

Williams and his research team, led by postdoctoral student Heidi Hofer, now an assistant professor at the University of Houston, used a laser-based system developed by Williams that maps out the topography of the inner eye in exquisite detail. The technology, known as adaptive optics, was originally used by astronomers in telescopes to compensate for the blurring of starlight caused by the atmosphere.

Williams turned the technique from the heavens back toward the eye to compensate for common aberrations. The technique allows researchers to study the living retina in ways that were never before possible. The pigment that allows each cone in the human eye to react to different colors is very fragile and normal microscope light bleaches it away. This means that looking at the retina from a cadaver yields almost no information on the arrangement of their cones, and there is certainly no ability to test for color perception. Likewise, the amino acids that make up two of the three different-colored cones are so similar that there are no stains that can bind to some and not others, a process often used by researchers to differentiate cell types under a microscope.

Imaging the living retina allowed Williams to shine light directly into the eye to see what wavelengths each cone reflects and absorbs, and thus to which color each is responsive. In addition, the technique allows scientists to image more than a thousand cones at once, giving an unprecedented look at the composition and distribution of color cones in the eyes of living humans with varied retinal structure.

Each subject was asked to tune the color of a disk of light to produce a pure yellow light that was neither reddish yellow nor greenish yellow. Everyone selected nearly the same wavelength of yellow, showing an obvious consensus over what color they perceived yellow to be. Once Williams looked into their eyes, however, he was surprised to see that the number of long- and middle-wavelength cones—the cones that detect red, green, and yellow—were sometimes profusely scattered throughout the retina, and sometimes barely evident. The discrepancy was more than a 40:1 ratio, yet all the volunteers were apparently seeing the same color yellow.

"Those early experiments showed that everyone we tested has the same color experience despite this really profound difference in the front-end of their visual system," says Hofer. "That points to some kind of normalization or auto-calibration mechanism—some kind of circuit in the brain that balances the colors for you no matter what the hardware is."

In a related experiment, Williams and a postdoctoral fellow Yasuki Yamauchi, working with other collaborators from the Medical College of Wisconsin, gave several people colored contacts to wear for four hours a day. While wearing the contacts, people tended to eventually feel as if they were not wearing the contacts, just as people who wear colored sunglasses tend to see colors "correctly" after a few minutes with the sunglasses. The volunteers' normal color vision, however, began to shift after several weeks of contact use. Even when not wearing the contacts, they all began to select a pure yellow that was a different wavelength than they had before wearing the contacts.

"Over time, we were able to shift their natural perception of yellow in one direction, and then the other," says Williams. "This is direct evidence for an internal, automatic calibrator of color perception. These experiments show that color is defined by our experience in the world, and since we all share the same world, we arrive at the same definition of colors."

Williams' team is now looking to identify the genetic basis for this large variation between retinas. Early tests on the original volunteers showed no simple connection among certain genes and the number and diversity of color cones, but Williams is continuing to search for the responsible combination of genes.


Story Source:

The above story is based on materials provided by University of Rochester. Note: Materials may be edited for content and length.


Cite This Page:

University of Rochester. "Color Perception Is Not In The Eye Of The Beholder: It's In The Brain." ScienceDaily. ScienceDaily, 26 October 2005. <www.sciencedaily.com/releases/2005/10/051026082313.htm>.
University of Rochester. (2005, October 26). Color Perception Is Not In The Eye Of The Beholder: It's In The Brain. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2005/10/051026082313.htm
University of Rochester. "Color Perception Is Not In The Eye Of The Beholder: It's In The Brain." ScienceDaily. www.sciencedaily.com/releases/2005/10/051026082313.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Mind & Brain News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Prenatal Exposure To Pollution Might Increase Autism Risk

Prenatal Exposure To Pollution Might Increase Autism Risk

Newsy (Dec. 18, 2014) Harvard researchers found children whose mothers were exposed to high pollution levels in the third trimester were twice as likely to develop autism. Video provided by Newsy
Powered by NewsLook.com
Yoga Could Be As Beneficial For The Heart As Walking, Biking

Yoga Could Be As Beneficial For The Heart As Walking, Biking

Newsy (Dec. 17, 2014) Yoga can help your weight, blood pressure, cholesterol and heart just as much as biking and walking does, a new study suggests. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins